Another option, although via a loophole, would be to purchase your own domain and create a forwarding email address. No matter what free email provider you have, if you'd ever change you just change the "forward to:" email address to which your forwarding address under your own domain sends the messages.
That way, you don't have to move your domain away from the DNS of your registrar and not worry about whether eg Gmail, Mail.ru, Yandex, etc will continue providing free mailboxes that allow using your own domain.
|